An electrical plug connected to an appliance is very often subjected to considerable forces, especially through the connecting lead cord or cable, when the user wishes to disconnect it from its socket. Indeed, present-day standards covering both plugs and sockets in practically all countries impose a minimum separation force for the withdrawal of a plug from its socket. All too often the user applies a greater separation force and, for reasons of convenience, applies this to the cord rather than to the plug, resulting in stretched, damaged or even broken conductors, creating a high risk of short-circuit and/or of electrocution. In other cases, particularly in the case of portable and/or mobile appliances, the user often tries to move as far away as possible by pulling on the cord rather than by plugging into a nearer socket, or may try to "remotely" disconnect the appliance by pulling on the cord; both of these practices present the same disadvantages and hazards as those stated above.
In addition, it is found that repeated removal of plugs from an electric socket weakens the mounting of the socket, again producing the same disadvantages and hazards.
Applicant's U.S. Pat. No. 5,171,291 describes a mechanical device facilitating the removal of an electrical plug from its socket by utilizing a thrust member fitted between the plug and the socket which is actuated by a control element mounted on the plug or on the socket and affords a suitable mechanical advantage to reduce the force required. However, while this device does greatly reduce the risks of short-circuit and/or electrocution, it requires the presence of the user close to the plugsocket connection in order to be actuated.
U.S. Pat. No. 4,045,106 describes an automatic disconnect system for an electrical plug which is remotely actuated by a pull on the power cable connected to the plug but requires the user to exert a force at least equal to the minimum separation force between the plug and a socket to activate the system. Moreover the system requires the power cable to pass through a sleeve forming a suitable angle with the plug support, which complicates its construction yet is operative only if the cable is moved laterally. Furthermore, the system increases very considerably the dimensions of the standard plug to which it is connected, since the plug slides inside a casing. In addition, the spring performing the disconnecting movement hampers the actuation of this movement so that a stable minimum limit for such actuation cannot be readily guaranteed, let alone adjusted to suit the manufacturer. Lastly, the conductors of the cable are bound to be weakened by their twisting movement in relation to their attachment.